# Digital power???

Started by February 26, 2005
```I've asked this before in a more complicated thread, and I guess I
everything else.  Cool Edit gives a result called "average RMS power",
which seems wrong on two counts.

1. "RMS power" is a misnomer.  Should be average power, which is merely
*determined* from RMS voltage (or amplitude, more generally?).

2. But what does power have to do with a digital signal in the first
place?  The digital signal represents a certain
voltage/pressure/whatever, but not necessarily a specific value (0 dBFS
could correspond to anything), and a corresponding power measurement
(power: the rate at which work is done) would also depend on load
resistance, etc.

Also, why is RMS written in lowercase everywhere?  Even Rane audio's
definition specifically states "lowercase".  It's an abbreviation!  I
don't get it!

--
Include "newsgroup" in the subject line to reply by email (or get dumped
with the spam).
```
```Jon wrote:

> I've asked this before in a more complicated thread, and I guess I
> everything else.  Cool Edit gives a result called "average RMS power",
> which seems wrong on two counts.
>
> 1. "RMS power" is a misnomer.  Should be average power, which is merely
> *determined* from RMS voltage (or amplitude, more generally?).

Correct.
>
> 2. But what does power have to do with a digital signal in the first
> place?  The digital signal represents a certain
> voltage/pressure/whatever, but not necessarily a specific value (0 dBFS
> could correspond to anything), and a corresponding power measurement
> (power: the rate at which work is done) would also depend on load
> resistance, etc.

If the digital signal is a linear representation of a real-world signal
then the "digital power" will be proportional to real power -- so if a
"digital power" of 0.1 (full scale)^2/sec generates a 2.5 watt output
then a "digital power" of 1.0 (full scale)^2/sec will generate 25 watts.

Your mention of dB_FS is more to the point: expressing gains and signal
levels in dB is extremely convenient in signal processing.  The fact
that it implies a power level may be confusing, but as I stated before
if the processing is all linear then you will ultimately be able to
equate it to an input power or an output power.
>
> Also, why is RMS written in lowercase everywhere?  Even Rane audio's
> definition specifically states "lowercase".  It's an abbreviation!  I
> don't get it!
>
Me neither.  I always use upper case.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
```
```Tim Wescott wrote:

> If the digital signal is a linear representation of a real-world signal
> then the "digital power" will be proportional to real power -- so if a
> "digital power" of 0.1 (full scale)^2/sec generates a 2.5 watt output
> then a "digital power" of 1.0 (full scale)^2/sec will generate 25 watts.

Ok, I kind of understand.

> Your mention of dB_FS is more to the point: expressing gains and signal
> levels in dB is extremely convenient in signal processing.  The fact
> that it implies a power level may be confusing, but as I stated before
> if the processing is all linear then you will ultimately be able to
> equate it to an input power or an output power.

Oh yeah, dB are technically related to power levels in the first place
(10*log10) and voltage decibels are a 20*log10 afterthought.  I assume
the dB I am using on screen are related to 20*log10, because they are
referring to amplitude levels.  Hmmm... but the "average RMS power" is
expressed in dB(FS?) as well.  Ok I think this is making some sense...

--
Include "newsgroup" in the subject line to reply by email (or get dumped
with the spam).
```
```Jon <u035m4i02@sneakemail.com> writes:
> [...]
> Also, why is RMS written in lowercase everywhere?  Even Rane audio's
> definition specifically states "lowercase".  It's an abbreviation!

I've always seen it in uppercase, and I vote we keep it in uppercase,
but there are some abbreviations that are lowercase, e.g., "e.g."
(exempli gratia).
--
%  Randy Yates                  % "Bird, on the wing,
%% Fuquay-Varina, NC            %   goes floating by
%%% 919-577-9882                %   but there's a teardrop in his eye..."
%%%% <yates@ieee.org>           % 'One Summer Dream', *Face The Music*, ELO
```
```Randy Yates wrote:
> Jon <u035m4i02@sneakemail.com> writes:
>
>>[...]
>>Also, why is RMS written in lowercase everywhere?  Even Rane audio's
>>definition specifically states "lowercase".  It's an abbreviation!
>
>
> I've always seen it in uppercase, and I vote we keep it in uppercase,
> but there are some abbreviations that are lowercase, e.g., "e.g."
> (exempli gratia).

Is "RMS" an acronym because it consists of initial letters of a phrase,
or something else because those letters are recited individually instead
of being pronounced as a word?

Jerry
--
Engineering is the art of making what you want from things you can get.
&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;
```
```Jerry Avins wrote:

> Randy Yates wrote:
>
>> Jon <u035m4i02@sneakemail.com> writes:
>>
>>> [...]
>>> Also, why is RMS written in lowercase everywhere?  Even Rane audio's
>>> definition specifically states "lowercase".  It's an abbreviation!
>>
>>
>>
>> I've always seen it in uppercase, and I vote we keep it in uppercase,
>> but there are some abbreviations that are lowercase, e.g., "e.g."
>> (exempli gratia).
>
>
> Is "RMS" an acronym because it consists of initial letters of a phrase,
> or something else because those letters are recited individually instead
> of being pronounced as a word?
>
Both abbreviations and acronyms should be written out with all caps --
although some acronyms get into lower case laser-quick; you have to keep
your radar screens in tune to find all the cases but even then you can
run into the occasional snafu.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
```
```Tim Wescott wrote:
> Both abbreviations and acronyms should be written out with all caps --
> although some acronyms get into lower case laser-quick; you have to
> keep your radar screens in tune to find all the cases but even then
> you can run into the occasional snafu.

ISTM that when on their own RMS, AC, DC etc. should be written in upper
case, but when used as qualifiers (Vrms, Vac, Vdc) they would normally be
written in lower case.

--
Martin

```
```On Sun, 27 Feb 2005 09:22:33 -0800, Tim Wescott
<tim@wescottnospamdesign.com> wrote:

>Jerry Avins wrote:
>
>> Randy Yates wrote:
>>
>>> Jon <u035m4i02@sneakemail.com> writes:
>>>
>>>> [...]
>>>> Also, why is RMS written in lowercase everywhere?  Even Rane audio's
>>>> definition specifically states "lowercase".  It's an abbreviation!
>>>
>>>
>>>
>>> I've always seen it in uppercase, and I vote we keep it in uppercase,
>>> but there are some abbreviations that are lowercase, e.g., "e.g."
>>> (exempli gratia).
>>
>>
>> Is "RMS" an acronym because it consists of initial letters of a phrase,
>> or something else because those letters are recited individually instead
>> of being pronounced as a word?
>>
>Both abbreviations and acronyms should be written out with all caps --
>although some acronyms get into lower case laser-quick; you have to keep
>your radar screens in tune to find all the cases but even then you can
>run into the occasional snafu.

Hi,

I recently had a big fight with the IEEE Sig. Proc.
magazine's publishing people.  I wanted the
abbreviation of "direct current", DC, to be printed
as upper case.  The magazine folk wanted it
printed in lower case.  (I was using the phrase DC to
indicate zero hertz.)   We argued and argued and then
they printed it as lower case.

[-Rick-]

```
```Martin Saxon wrote:
> ISTM that when on their own RMS, AC, DC etc. should be written in upper
> case, but when used as qualifiers (Vrms, Vac, Vdc) they would normally be
> written in lower case.

Those are just a substitute for subscripts.  If you have the typography
available, they would be V<sub>AC</sub>, V<sub>CC</sub>, etc.

--
Include "newsgroup" in the subject line to reply by email (or get dumped
with the spam).
```
```Tim Wescott wrote:

>
> Both abbreviations and acronyms should be written out with all caps --
> although some acronyms get into lower case laser-quick; you have to keep
>